Ultem PEI (Polyetherimide): High-Temperature Amorphous Thermoplastic Properties
Published: 2026-05-25
Polyetherimide (PEI), best known by Sabic's trade name Ultem, is an amorphous high-performance thermoplastic offering an exceptional balance of high strength, inherent flame retardancy (UL94 V-0 without additives), excellent dielectric...
Polyetherimide (PEI), best known by Sabic's trade name Ultem, is an amorphous high-performance thermoplastic offering an exceptional balance of high strength, inherent flame retardancy (UL94 V-0 without additives), excellent dielectric properties, and broad chemical resistance. Its glass transition temperature of 217°C makes it suitable for applications from -40°C cryogenic to hot-water/steam environments. It is widely used in medical devices (autoclavable surgical instrument handles), aerospace interiors (low smoke, low toxicity), electrical/electronic connectors, and semiconductor wafer handling components.
Unlike semicrystalline PEEK, PEI is amorphous—it does not have a melting point and transitions gradually through its glass transition. This provides advantages in dimensional stability (low and isotropic shrinkage) and eliminates the crystallinity-dependent properties that complicate PEEK processing. However, PEI has lower chemical resistance than PEEK (particularly to chlorinated solvents and strong bases) and lower continuous service temperature. PEI must be dried to <0.02% moisture before processing; inadequate drying causes splay, silver streaks, and part brittleness.
Reinforced grades: Ultem 2300 (30% glass fiber) increases tensile strength to 140 MPa and HDT to 210°C. Ultem 4000 series adds internal mold release for improved cycle times in high-cavitation tooling.
Technical Properties
| Density | 1.27 g/cm³ |
|---|---|
| Tensile Strength | 105 MPa |
| Melting Point | N/A (Amorphous, Tg 217°C) |
| Shrinkage Rate | 0.5-0.7% |
| Flexural Modulus | 3.5 GPa |
| Hdt | 200 °C at 1.82 MPa |
| Continuous Service Temp | 170 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Sabic Ultem 1000 | |
| Ultem 2300 (30% GF) | |
| RTP 2100 Series |
Frequently Asked Questions
What is the critical drying requirement for Ultem PEI?
PEI must be dried to a moisture content below 0.02% (200 ppm) before injection molding. The recommended drying conditions are 150°C (300°F) for 4-6 hours in a desiccant dryer with a dew point of -30°C or lower. Inadequate drying is the #1 cause of processing defects in PEI—moisture hydrolyzes the polymer chains at melt temperature (350-400°C), causing splay (silver streaks), reduced mechanical properties, and brittle parts. A properly dried PEI granulate should show no moisture condensation when placed in a sealed jar and cooled.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org